Coaxial cables generally include an inner conductor for signal transmission, surrounded by an inner insulative layer around which is an outer conductor concentric with the inner conductor, and the cable also has an outer insulative jacket therearound. For enabling connection of the coaxial cable to a device, or to another coaxial cable, a connector is required which includes an inner contact or terminal mechanically and electrically connected to an end of the inner conductor, a dielectric sleeve therearound, and an outer conductor or contact which is mechanically and electrically connected to the shielding braid of the cable. Such mechanical and electrical connection of the inner and outer contacts of the connector to the inner and outer conductors of the cable must be made in such a way that minimizes impedance mismatch which otherwise would degrade the signal being transmitted. Such degradation is the result of discontinuities in the radial distance between the outer surface of the inner contact and the inner surface of the outer contact which generates reflections into the circuit, which discontinuities include changes in diameter in either contact or deformation of the metal and which is influenced by the distance of such diameter change from the mating interface with inner and outer contacts of a mating coaxial connector.
Commonly such mechanical and electrical connection of at least the signal or inner contact to the inner conductor is established by soldering the contact to an exposed end of the cable's inner conductor. As is typical of soldering operations generally, such procedures are time-consuming and are technique sensitive, in order to provide an assured solder joint; additionally, soldering is subject to outside influences which can affect the integrity of the resulting joint such as a layer of incremental corrosion upon one or both metal surfaces, and the freedom from impurities in the solder or flux or the assembly area. Further, inspection of the finished solder joint is required to provide visual verification of the quality of the joint, prior to completion of the process of affixing the connector to the cable end, whereafter the solder joint is hidden.
It is known to terminate the conductor of a wire, other than coaxial cable, by exposing a length of the conductor, inserting the exposed length into the wire-receiving barrel of an electrical terminal, and crimping the barrel to the wire by deforming the malleable metal radially inwardly under such pressure along a limited axial distance to in turn deform the malleable (usually high copper content alloy) metal of the conductor, creating compressively interfitting metal/metal formations defining a crimp joint which thereafter remains in such deformed condition with the metal of the terminal assuredly electrically connected to the metal of the conductor.
For example, see AMP Instruction Sheet IS 7516 dated Dec. 3, 1990 entitled "AMP Screw-Machine Contacts and Application Tooling." For coaxial cable terminals and connectors in particular, see AMP Instruction Sheet IS 2348-2 dated Mar. 29, 1974 and entitled "AMP COAXICON Contacts", and also AMP Instruction Sheet IS 2987-3 dated Aug. 20, 1991 entitled "AMP Coaxial RF Series 50-Ohm and 75-Ohm Commercial SMB Bulkhead Jack Connectors."
Tools are also known which perform the crimping operation, having dies which are pressed against the outside of the terminal barrel generally at several spaced circumferential locations therearound to deform the metal thereof radially inwardly. A variety of shapes of crimping dies are known which provide an optimum crimp joint for the particular gage of wire, the particular single-strand or multi-strand composition of the wire's conductor, the type of metal of the conductor and the terminal barrel, and the difference in diameters therebetween, and so on. One such tool is sold by Daniels Manufacturing Corp. under Part No. AFM8 (M22520/2-01).
Standards for such tools and a variety of positioner attachments is disclosed in Military Specification MIL-C-22520/2C dated Mar. 19, 1976. A particular positioner is selected according to the size terminal to be crimped, and is affixed to the crimping tool opposed from the crimping port into which the terminal will be placed, in such a manner that a terminal-receiving aperture is aligned with the crimping port to receive the terminal and thereafter hold it in position for wire end insertion and the crimping of the terminal to the wire end.
It is desired to provide a method of and apparatus for securing an electrical terminal to a coaxial cable's inner conductor which does not involve soldering.
It is further desired that such method reliably result in a mechanical and electrical connection which minimizes impedance mismatch.
It is additionally desired to provide a connector and terminal and apparatus especially suited for such method.